The Human Nervous System Slide # 1 Dr. Rufus Weaver shows “Harriet.” Harriet Cole was a cleaning woman at the medical college where Dr. Weaver taught. When Miss Cole died, she donated her body to the study of science. Dr. Weaver spent 8-10 hours a day for 5 months dissecting Harriet’s body. He removed all of the soft tissue and bones and left only the eyes and the nervous system. He preserved the nervous system by coating the nerves and eyes with white lead-based paint and shellac. Circa 1888

1. Major controlling, regulatory, and communicating system in the body 2. Center of all mental activity including thought, learning, and memory 3. Together with the endocrine system, the nervous system is responsible for regulating & maintaining homeostasis. 4. Responds to internal and external stimuli Slide # 2 Our nervous system allows us to feel pain. Functions of the Nervous System

Structure 1. Consists of nerve cells called neurons. 2. Neurons are specialized for transmitting electrical signals called nerve impulses. Slide # 3

Neurons 3 Types of Neurons 1. Sensory: carry impulses from sense organs to spinal cord & brain 2. Motor: carry impulses from the brain & spinal cord to muscles & glands 3. Interneurons: connected to sensory & motor neurons & carry impulses between them Slide # 3 Neurons from cow brain

1. Cell body: contains nucleus & most of the cytoplasm 2. Dendrites: carry impulses from the environment or other nerve cells to the cell body 3. Axon: carries impulses away from cell body 4. Myelin sheath: covers most axons 5. Nodes: gaps; axon membrane exposed 6. Axon terminals: direct impulses to another neuron or other cell Slide # 4 Parts of a Typical Neuron

TAKS Practice The arrows in Figure X show— A. Movement of a stimulus in a cyton B. Transport of oxygen in a nerve C. Transfer of an impulse from one neuron to another neuron D. Response of an effector to a stimulus Figure X What is this diagram showing? Movement of message along nerves Correct answer: C

Three Types of Neurons Types of Neurons 1.Sensory: send messages from the body to the brain 2. Interneurons: connect sensory & motor neurons at the spinal cord 3. Motor: send messages from the brain to the body (muscles) Slide # 4 Neurons from cow brain

Nerves and Muscles Nerves work together with muscles for movement. An Impulse begins when one neuron is stimulated by another neuron or by the sense organs. The impulse travels down the axons of sensory neurons to interneurons in the spinal cord and brain. The brain will then send an impulse through motor neurons to the necessary muscle or organ, telling it to contract. Sensory neuron Motor neuron Interneuron

Reflex Arc A reflex is an involuntary response that is processed in the spinal cord, not the brain. This is why you react first and then feel the pain.

Multiple Sclerosis Cause: 1. Destruction of large patches on the myelin sheath of the neuron. 2. Small, hardened scars appear along the axon which interferes with the normal transmission of impulses. Results: 1. Normal nerve function is slowed 2. Symptoms such as double vision, muscular weakness, loss of memory, and paralysis result

Two Main Divisions of the Nervous System: CNS and PNS A B C D A.Cerebrum: Voluntary or conscious activities of the body B.Cerebellum: Coordinates & balances the actions of the muscles C.Medulla Oblongata (brainstem): Connects the brain & spinal cord. Controls autonomic functions such as breathing, digestion, heart rate, blood vessel function, swallowing and sneezing. Regulates the flow of information between the brain & the rest of the body D.Spinal Cord: The main communications link between the brain & the rest of the body

Divisions of the Nervous System 1.Central Nervous System (CNS) a. Consists of brain & spinal cord b. Functions: relays messages, processes information, and analyzes information 2.Peripheral Nervous System a. Relays messages from body to brain b. Transmits commands from brain to body Slide # 7

Parts of The Spinal Cord pairs of spinal nerves connect brain to rest of body a. cervical nerves: 8 pair Injuries in this area usually result in quadriplegia or paraplegia b. thoracic nerves: 12 pair Control chest and abdominal muscles c. lumbar nerves: 5 pair Control leg muscles d. sacral nerves: 5 pair Control bowel and bladder functions e. coccygeal nerves: 1 pair Slide # 14

The Brain 1. Cerebrum: responsible for voluntary or conscious activities of the body –Center for intelligence, learning & judgment 2. Cerebellum: coordinates & balances the action of muscles; allows body to move gracefully & efficiently 3. Brain stem: connects brain & spinal cord 4. Thalamus: receives messages from all sensory receptors throughout body –Relays information to cerebrum Slide # Hypothalamus: control center for recognition & analysis of hunger, thirst, fatigue, anger, & body temperature.